If I'm doing it out of the kindness of my heart (aka the players are taking way too long to solve what should be a relatively easy problem and I'm getting impatient), I'll give them exactly what they need to get through the problem.

I usually would have things pre-placed in advance. Especially if they are going to be needed for something and there's a chance a party member wouldn't have the skill/spell to do it. But that doesn't always mean the players will find it or even look for it.

If it's just random loot time, I use the tables and roll dice for it.